JP6810887B2 - Separation and recovery methods for selenium, tellurium, and platinum group elements - Google Patents

Description

The present invention relates to a treatment method for efficiently separating and recovering selenium, tellurium, and platinum group elements contained in a liquid after extracting gold from a decopper electrolytic slime leachate.

In the copper electrolysis process in the copper smelting process, copper electrolysis slime is produced as a by-product. This copper electrolytic slime contains a trace amount of precious metals such as gold, silver and platinum group elements together with copper, and further contains selenium and tellurium. Therefore, in order to recover the precious metal, it is necessary to separate selenium and tellurium contained as impurities.

As a method for separating selenium and tellurium from a platinum group element, the method described in Non-Patent Document 1 is known. In this method, gold, a platinum group element, selenium, and tellurium are leached by decopperation treatment of copper electrolytic slime and then chloride leaching treatment, and the leachate is brought into contact with an extraction solvent to extract gold. Next, sulfite gas is blown into the liquid after gold extraction to recover selenium, tellurium and platinum group elements as a reducing slag, and selenium is distilled and separated from the reducing slag to recover the distillation residue containing tellurium and platinum group elements. To do.

In the above treatment method of Non-Patent Document 1, when selenium is distilled and purified by heating a reducing selenium containing selenium, tellurium and a platinum group element, the content of tellurium in the distilled selenium becomes high, and high-grade selenium is produced. There was a difficulty that it could not be collected. Therefore, a treatment method in which the reducing slag is formed stepwise to separate and recover selenium and the like (Patent Document 1), a treatment method in which the reducing slag is alkali-melted to separate selenium and a platinum group element (Patent Document 2). A treatment method (Patent Document 3) is known in which the reducing slag is oxidatively roasted to separate selenium and then alkaline leached or alkaline melted to separate tellurium and a platinum group element.

Specifically, in the treatment method described in Patent Document 1, the chlorine ion concentration is controlled to 1.5 mol / L or less when the sulfite gas is blown into the liquid after gold extraction to form a reducing slag. While suppressing the precipitation of selenium and tellurium, the platinum group element was separated into a reducing slag, and then sulfite gas was further blown into the separated liquid to reduce the chlorine ion concentration to 2 mol / L or less and in the liquid. The concentration of selenium is controlled to 3 g / L or more to suppress the reduction of tellurium, and selenium is used as a reducing residue for separation. Further, sulfur dioxide gas is further blown into the separated liquid of the reducing slag to turn tellurium into a reducing slag for separation.

In the treatment method described in Patent Document 2, after sulfite gas is blown into the liquid after gold extraction to form a reducing slag containing selenium, tellurium, and platinum group elements, a mixed flux of caustic soda and sodium nitrate is formed in the reducing slag. Is added and heated and melted, and this melt is leached with water to separate it into a liquid containing sodium selenate and a residue containing a platinum group element, and the platinum group element of the residue is recovered by leaching with hydrochloric acid oxidation. ..

In the treatment method described in Patent Document 3, a solution containing selenium, tellurium and platinum group elements such as a liquid after gold extraction is reduced to form a reducing slag in which selenium, tellurium and platinum group elements are concentrated. After the reducing slag is oxidatively roasted to selectively volatilize and separate selenium, the roasting residue is leached with alkali to leach tellurium, or a combination of alkali melting and water leaching is performed, and platinum remaining in the leaching residue is performed. Recover group elements.

Japanese Unexamined Patent Publication No. 2001-316735 Japanese Unexamined Patent Publication No. 2003-268457 Japanese Unexamined Patent Publication No. 2016-160479

J. E. Hoffmann et al., Proceeding of Copper 95- Cobre 95 International Conference

The treatment method of Patent Document 1 has many parameters at the time of selenium reduction such as hydrochloric acid concentration, temperature, sulfurous acid gas concentration, and sulfur dioxide gas amount, so that it is difficult to control, and the recovery rate of platinum group elements, selenium, and tellurium is lowered. There's a problem. In the treatment method of Patent Document 2, a reducing slag containing selenium, tellurium, and a platinum group element is alkali-melted and leached with water, and selenium is made into a sodium selenate leachate and separated from a residue containing a platinum group element. Then, tellurium becomes difficult to exude and remains together with the platinum group element, so it takes time and effort to separate the platinum group element and tellurium. Similarly, the treatment method of Patent Document 3 has a problem that tellurium is difficult to leached when the oxidative roasting residue is directly alkali-melted.

The treatment method of the present invention solves the above-mentioned problems in the treatment methods described in Patent Documents 2 and 3 by oxidatively roasting reducing slag and the like, leaching the roasted residue with alkali, and then melting the roasted residue with alkali. Further, unlike the treatment method that is difficult to control as in Patent Document 1, a treatment method is provided in which the separability between tellurium and platinum group elements is good, the leaching rate of tellurium and platinum group elements is high, and the recovery rate of these is high. ..

The present invention relates to a method for separating and recovering selenium, tellurium, and a platinum group element having the following constitutions.
[1] In a method for separating and recovering selenium, tellurium, and platinum group elements from a roasting raw material containing metallic selenium, tellurium, and platinum group elements.
An oxidative roasting step in which the roasting raw material is heated in an oxidizing atmosphere to selectively volatilize selenium, an alkaline leaching step in which the oxidative roasting residue is added to an alkaline solution to leach tellur, and an alkaline substance flux in the alkaline leaching residue. It has an alkali melting step of adding and heating and melting, and a hydrochloric acid oxidation leaching step of adding an oxidizing agent and hydrochloric acid to the alkaline melt to leach platinum group elements.
In the oxidative roasting step, the roasting raw material is heated to 400 ° C. to 550 ° C. to selectively volatilize selenium, and in the alkali leaching step, the oxidative roasting residue is suspended in an alkaline solution to pH 13 or higher. Tellurium is leached and separated into solid and liquid, and the alkali leaching residue containing the tellurium leaching solution and platinum group elements is recovered. In the alkali melting step, the mixture of the alkali leaching residue and the flux is heated to 350 ° C. to 500 ° C. A method for separating and recovering selenium, tellurium, and platinum group elements, which comprises performing alkali melting.
[2] The above-mentioned [1], wherein either or both of sodium hydroxide and sodium nitrate are used as the flux in the alkali melting step, and the amount of the flux is 1 to 3 times the weight ratio of the alkali leaching residue. Separation and recovery method.
[3] Described in any of the above [1] or [2], wherein the free chlorine concentration is 4 mol / L to 6 mol / L and the liquid temperature is 60 ° C. to 70 ° C. in the hydrochloric acid oxidation leaching step. Separation and recovery method.
[4] The separation and recovery method according to any one of the above [1] to [3], wherein the roasting raw material is a reduction slag obtained by reducing a solution containing selenium, tellurium, and a platinum group element.

Hereinafter, the processing method of the present invention will be specifically described.
The treatment method of the present invention is a method for separating and recovering selenium, tellurium, and platinum group elements from a roasting raw material containing metallic selenium, tellurium, and platinum group elements.
An oxidative roasting step in which the roasting raw material is heated in an oxidizing atmosphere to selectively volatilize selenium, an alkaline leaching step in which the oxidative roasting residue is added to an alkaline solution to leach tellur, and an alkaline substance flux in the alkaline leaching residue It has an alkali melting step of adding and heating and melting, and a hydrochloric acid oxidation leaching step of adding an oxidizing agent and hydrochloric acid to the alkaline melt to leach platinum group elements.
In the oxidative roasting step, the roasting raw material is heated to 400 ° C. to 550 ° C. to selectively volatilize selenium, and in the alkaline leaching step, the oxidative roasting residue is suspended in an alkaline solution to pH 13 or higher. Tellurium is leached and separated into solid and liquid, and the alkali leaching residue containing the tellurium leaching solution and platinum group elements is recovered. In the alkali melting step, the mixture of the alkali leaching residue and the flux is heated to 350 ° C. to 500 ° C. It is a method for separating and recovering selenium, tellurium, and platinum group elements, which comprises performing alkali melting. The outline of the processing method of this invention is shown in FIG.

[Roasting ingredients]
As a roasting raw material, a reducing slag obtained by reducing a solution containing selenium, tellurium, and a platinum group element can be used. For example, after extracting gold from the chloride leachate of decopper electrolytic slime, the liquid contains a large amount of selenium, tellurium, and platinum group elements. A reducing agent may be added to a solution containing selenium, tellurium, and a platinum group element and stirred to reduce the selenium, tellurium, and platinum group elements in the solution. As the reducing agent, sulfur dioxide gas, sodium hydrogen sulfite solution and the like can be used. The liquid temperature of the reduction treatment is preferably heated to 70 ° C. to 80 ° C. By this reduction treatment, selenium, platinum group elements, and tellurium contained in the above-mentioned liquid are reduced to metal and precipitated to form a reducing slag.

[Oxidation roasting]
The roasting raw material such as the reducing slag is oxidatively roasted to volatilize selenium, while tellurium and platinum group elements are left in the roasting residue. Oxidative roasting is preferably performed at a roasting temperature of 400 ° C. to 550 ° C. under air or air circulation. If the roasting temperature is 600 ° C. or higher, the platinum group elements are oxidized and insolubilized in the leaching step of the post-treatment, which is not preferable. If the roasting temperature is lower than 400 ° C, selenium will not vaporize sufficiently. As for the roasting time, if the concentration of the selenium dioxide gas produced decreases and reaches a plateau, the roasting may be completed.

By oxidative roasting, selenium contained in the raw material produces selenium dioxide and vaporizes. This selenium dioxide gas can be passed through an aqueous solution of caustic soda to generate selenite soda, and the selenite soda can be reduced to recover metallic selenium. On the other hand, tellurium becomes an oxide, but tellurium dioxide hardly vaporizes in the above temperature range, so that it becomes a roasted residue together with platinum group elements. By oxidative roasting in this way, selenium can be separated from tellurium and platinum group elements.

[Alkaline leaching]
The oxidative roasted residue contains tellurium oxide and platinum group elements. The roasted residue is leached with alkali to recover tellurium. For example, tellurium is leached by mixing the oxidative roasted residue with an alkaline solution such as caustic soda solution. This alkali leaching is preferably under strong alkali with a pH of 13 or higher. Tellurium oxide contained in the roasted residue is mainly tetravalent, and forms tellurous acid ions and elutes under strong alkali. The liquid temperature for alkali leaching is preferably 25 ° C to 50 ° C.

Tellurium elutes into the liquid due to alkali leaching, and platinum group elements such as rhodium and palladium remain uneluted. Since selenium is first separated by oxidative roasting, only tellurium can be selectively eluted. This is filtered off to collect the tellurium leachate, and the tellurium leachate is neutralized by adding sulfuric acid or hydrochloric acid to form a tellurium dioxide precipitate. The grade of this tellurium dioxide is about 99% by mass or more, and high-grade tellurium dioxide can be recovered.

[Alkaline melting]
Alkali melting is performed by adding a flux of an alkaline substance to the alkali leaching residue. It is preferable to use either or both of sodium hydroxide and sodium nitrate as the flux. In addition, sodium carbonate and sodium peroxide can be used as the flux. The amount of flux is preferably 1 to 3 times the weight ratio of the alkali leaching residue. The melting temperature is preferably 350 ° C. to 500 ° C., and it may be melted by heating for 5 to 7 hours.

By alkali melting, the metallic platinum group element contained in the alkali leaching residue becomes an alkali composite, for example ruthenium, in the form of sodium ruthenium acid, and is easily leached by the hydrochloric acid oxidation treatment in the next step. This alkali melting is preferably performed after alkali leaching. If the oxidative roasting residue is subjected to alkaline melting without alkali leaching, most of the tellurium oxide contained in the oxidative roasting residue becomes hexavalent, so that tellurium is less likely to leached into water after the alkali melting, and the melt Almost never seeps into water.

When selenium oxide remains in the alkaline melt, selenium oxide can be leached and separated by leaching the alkaline melt with water. This water leaching may be carried out by adding water to the alkali melt residue to form a slurry and heating the slurry at 70 ° C. to 90 ° C. for 0.5 to 2 hours. When the alkaline melt contains almost no selenium oxide or the like, water leaching may be omitted and hydrochloric acid oxidative leaching may be performed in the next step.

[Hydrochloric acid oxidative leaching]
Since the alkaline melt contains platinum group elements, an oxidizing agent such as hydrogen peroxide is added to the melt together with hydrochloric acid and heated to elute the platinum group elements. By this hydrochloric acid oxidative leaching (chlorination), the platinum group elements form a chloride complex and elute. Hydrochloric acid oxidative leaching is preferably in the range where the free chlorine concentration in the liquid is 4 mol / L to 6 mol / L, and the liquid temperature is preferably 60 ° C. to 75 ° C. If the hydrochloric acid concentration is lower than the above range, the platinum group elements will not be sufficiently leached, while if the hydrochloric acid concentration is higher than the above range, the equipment will be significantly corroded and the filterability of the liquid will be reduced. Becomes difficult.

When an ammonium chloride solution is added to a leachate containing a platinum group chloride complex, platinum forms ammonium chloride and selectively precipitates. Therefore, this precipitate is filtered off and heated to 800 ° C to 950 ° C. Metallic platinum can be recovered.
In addition, palladium and the like remain in the filtrate from which ammonium chloride ammonium chloride is separated, and when ammonia water is added to this filtrate, a precipitate containing palladium is formed. When this is recovered and heated to 800 ° C. or higher, a sponge-like metal is formed. Palladium can be obtained. Rhodium and ruthenium can also be purified and recovered by a known method.

According to the treatment method of the present invention, selenium, tellurium, and platinum group elements can be efficiently separated and recovered from the reducing slag obtained by reducing the gold-extracted liquid of the chloride leachate of the decopper electrolytic slime. The treatment method of the present invention has good separability of selenium, tellurium, and platinum group elements. Specifically, in the treatment method of the present invention, selenium is selectively vaporized by oxidative roasting to separate tellurium and platinum group elements, so that high-purity selenium that does not contain tellurium and platinum group elements can be recovered. it can.

Further, in the treatment method of the present invention, the leaching rate of tellurium can be increased because the oxidative roasted residue from which selenium is separated is leached with alkali to elute tellurium. Further, since selenium is first separated by oxidative roasting, a tellurium leaching solution in which selenium is not mixed can be obtained by alkaline leaching, and high-purity tellurium can be recovered.

Further, in the treatment method of the present invention, after alkali leaching, the leaching residue is alkali-melted to make the platinum group elements contained in the leaching residue easy to leached by hydrochloric acid oxidation, so that the recovery rate of the platinum group elements can be increased. it can. In addition, since selenium and tellurium are separated by hydrochloric acid oxidative leaching, high-purity platinum group elements can be recovered.

A process diagram showing an outline of the processing process of the present invention.

Hereinafter, examples of the present invention will be shown together with comparative examples. Concentrations of selenium, tellurium and platinum group elements were measured by ICP-AES.

[Example 1]
100 g of the roasting raw material was oxidatively roasted for 4 hours under the conditions of a roasting temperature of 450 ° C. and an oxygen flow rate of 1 L / min. To obtain a roasted residue. The amount of selenium in the roasted residue was 870 mg, and the selenium removal rate was 99% or more. The roasted residue was suspended in 30 mL of an aqueous NaOH solution (NaOH concentration 5 mol / L) at 25 ° C. to 50 ° C., tellurium was leached, and solid-liquid separation was obtained to obtain an leaching slag. The leaching residue, caustic soda, and sodium nitrate were mixed so as to have a weight ratio of 7: 5: 5, and alkali melting was performed at 400 ° C. for 2 hours. The obtained melt was immersed in distilled water at room temperature for water leaching. Hydrogen peroxide solution and hydrochloric acid were added to the water leaching residue so that the free chlorine concentration became 5 mol / L, and the mixture was heated to 60 to 75 ° C. for hydrochloric acid oxidative leaching. After this leaching, solid-liquid separation was performed to obtain an leaching solution and an leaching residue.
Table 1 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in roasting raw materials, alkaline leachate, alkaline leachate, alkaline melt, water leachate, water leachate, hydrochloric acid oxidation leachate, and hydrochloric acid oxidation leachate. It was.
The leaching rate was calculated by the following formula. It is desirable that the leaching rate is high, and in particular, the platinum group element is desirable to have a high leaching rate in order to suppress the transfer to the hydrochloric acid oxidation leaching residue as much as possible.
Leachage rate of component X (%) = (content of component X in hydrochloric acid oxidation leachate / (content of component X in hydrochloric acid oxidation leachate + content of component X in hydrochloric acid oxidation leachate) x 100

[Example 2]
Oxidation roasting, alkali leaching, alkali melting, water leaching, and hydrochloric acid oxidative leaching were performed in the same manner as in Example 1 except that the oxidative roasting temperature was changed to 550 ° C. and the alkaline molten metal temperature was changed to 500 ° C. Table 2 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Example 3]
Oxidation roasting, alkali leaching, alkali melting, water leaching, and hydrochloric acid oxidative leaching were performed in the same manner as in Example 1 except that the oxidative roasting temperature was changed to 400 ° C. and the alkali melting temperature was changed to 350 ° C. Table 3 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Example 4]
Oxidation roasting, alkali leaching, alkali melting, water leaching, and hydrochloric acid oxidative leaching were performed in the same manner as in Example 1 except that the amount of flux in alkali melting was increased by 1 to 3 times. Tables 4 and 5 show the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Example 5]
Oxidative roasting, alkali leaching, alkali melting, water leaching, and hydrochloric acid oxidative leaching were carried out in the same manner as in Example 1 except that the free chlorine concentrations in hydrochloric acid oxidative leaching were set to 4 mol / L and 6 mol / L. Tables 6 and 7 show the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Comparative Example 1]
Oxidation roasting, alkali leaching, alkali melting, water leaching, and hydrochloric acid oxidative leaching were performed in the same manner as in Example 1 except that the oxidative roasting temperature was changed to 600 ° C. Table 8 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Comparative Example 2]
Oxidation roasting, alkali leaching, and hydrochloric acid oxidative leaching were performed in the same manner as in Example 1 except that the oxidative roasting temperature was changed to 600 ° C., alkali leaching and water leaching were not performed, and the alkali leaching residue was oxidatively leached with hydrochloric acid. .. Table 9 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and leaching residue after hydrochloric acid oxidative leaching.

[Comparative Example 3]
Oxidative roasting, alkali leaching, and hydrochloric acid oxidative leaching were carried out in the same manner as in Example 1 except that the alkaline leaching residue was oxidatively leached with hydrochloric acid without alkali melting and water leaching. Table 10 shows the amounts and leaching rates of selenium, tellurium, and platinum group elements contained in the leaching solution and the leaching residue after hydrochloric acid oxidative leaching.

[Comparative Example 4]
After oxidative roasting in the same manner as in Example 1, alkali melting was performed on the roasted residue in the same manner as in Example 1 without alkali leaching. This melt was leached with distilled water, but the melt was hardly dissolved in water and could not be used for hydrochloric acid oxidative leaching in the next step.

[Comparative Example 5]
100 g of the same roasting raw material as in Example 1 was roasted by oxidation for 4 hours under the conditions of a roasting temperature of 350 ° C. and an oxygen flow rate of 1 L / min. However, the roasting did not proceed and the raw material adhered to the crucible. It was.

Claims (4)

In a method for separating and recovering selenium, tellurium, and platinum group elements from roasting raw materials containing metallic selenium, tellurium, and platinum group elements.
Oxidation roasting step of selectively volatilize selenium and heating the roasted material in an oxidizing atmosphere, alkaline leaching step of leaching of tellurium by adding oxidizing roasting residue in an alkaline solution, the flux of alkaline material in an alkaline leach residue It has an alkali melting step of adding and heating and melting, and a hydrochloric acid oxidation leaching step of adding an oxidizing agent and hydrochloric acid to the alkaline melt to leach platinum group elements.
In the oxidation roasting step, the roasting material was selectively volatilize selenium was heated to 400 ° C. to 550 ° C., in the alkali leaching process, pH 13 or higher by the oxidation roasting residue was suspended in an alkaline solution in tellurium and solid-liquid separation by leaching to recover the alkali leaching residue containing tellurium leachate and a platinum group element, in the alkali melt process, by heating a mixture of the alkali leach residue and flux to 350 ° C. to 500 ° C. A method for separating and recovering selenium, tellurium, and platinum group elements, which comprises performing alkali melting. The separation and recovery method according to claim 1, wherein either or both of sodium hydroxide and sodium nitrate are used as the flux in the alkali melting step, and the amount of the flux is 1 to 3 times the weight ratio of the alkali leaching residue. .. The separation and recovery method according to claim 1 or 2, wherein in the hydrochloric acid oxidative leaching step, the free chlorine concentration is 4 mol / L to 6 mol / L and the liquid temperature is 60 ° C. to 70 ° C. The separation and recovery method according to any one of claims 1 to 3 , wherein the roasting raw material is a reduction slag obtained by reducing a solution containing selenium, tellurium, and a platinum group element.

Images